When producing a semiconductor substrate, various materials including both organic materials and inorganic materials are used, and tungsten and titanium nitride are included therein. Tungsten is used, for example, as a wiring material. Regarding titanium nitride, recently, methods for using it as a hard mask have been examined.
For example, in the case of a semiconductor substrate in which tungsten coexists with titanium nitride on the surface of the substrate, wherein tungsten is used as a wiring and titanium nitride is used as a hard mask, it is desired to remove titanium nitride without corroding tungsten. Titanium nitride can be relatively easily removed by using a composition containing hydrogen peroxide, but it is difficult to use hydrogen peroxide because it has high tungsten corrosiveness. In addition, it is required to increase the etching selectivity of titanium nitride relative to tungsten.
For this reason, in order to prevent tungsten corrosion due to hydrogen peroxide, methods of adding a corrosion preventer to a composition containing hydrogen peroxide have been examined. Patent Document 1 discloses corrosion preventers obtained by using quaternary ammonium and salts thereof, quaternary pyridinium and salts thereof, quaternary bipyridinium and salts thereof, and quaternary imidazolium and salts thereof. However, the corrosion preventers disclosed in Patent Document 1 do not exert sufficient effects of preventing corrosion of tungsten.
Patent Document 2 describes that titanium nitride can be etched without corroding tungsten by using a concentrated sulfuric acid as a composition not containing hydrogen peroxide. However, in Patent Document 2, the etching rate of titanium nitride is low (3 to 15 Å/min). Therefore, it is not practical, for example, in the case of use for removing a titanium nitride hard mask, which usually has a thickness of several hundred Å to several thousand Å.
Patent Document 3 describes that titanium nitride can be etched without corroding tungsten by using a composition containing an oxidizing agent, a fluorine compound and a corrosion preventer. However, in Patent Document 3, titanium nitride removability is low, and for example, there is a problem that sufficient effects of preventing tungsten corrosion are not obtained thereby.